Quality of life things

Make a couple improvements to the game:

1. A play button right from the slot screen (so you can get straight into the game). The previous flow meant you had to go into the slot edit screen to play, even if you didn't want to change the slot. This makes the process to play a game 2 clicks.
2. Directionality on the player, so I can select a different set of sprites depending on which direction the player last walked in.